为 List.Any(v => v.Contains(Book.Title.ToString())) 生成表达式树

Question

正如标题所说，如果字符串列表中的任何项目与一本书的字符串匹配，我正在尝试生成一个表达式树来检查 object。

到目前为止我得到了这个：

private static Expression<Func<Books, bool>> GenerateListContainsLikeExpression(string propertyName, List<string> values)
    {
        var parameter = Expression.Parameter(typeof(Books), "b");
        var listParameter = Expression.Parameter(typeof(string), "v");
        var property = Expression.Property(parameter, propertyName);
        var anyMethod = typeof(Enumerable).GetMethods(BindingFlags.Static | BindingFlags.Public).First(m => m.Name == "Any" && m.GetParameters().Count() == 2).MakeGenericMethod(typeof(string));
        var toStringMethod = typeof(object).GetMethod("ToString");
        var containsMethod = typeof(string).GetMethod("Contains");
        var objectString = Expression.Call(property, toStringMethod);
        var lambda = Expression.Call(listParameter, containsMethod, objectString);
        var func = Expression.Lambda<Func<List<string>, bool>>(lambda, parameter);
        var comparison = Expression.Call(anyMethod, Expression.Constant(values), func);

        return Expression.Lambda<Func<Books, bool>>(comparison, parameter);
    }

但是我收到这个错误：

Expression of type 'System.Boolean' cannot be used for parameter of type 'System.Func2[System.String,System.Boolean]' of method 'Boolean Any[String](System.Collections.Generic.IEnumerable1[System.String], System.Func`2[System.String,System.Boolean])'

在这一行：

var comparison = Expression.Call(anyMethod, Expression.Constant(values), lambda);

我觉得我只需要最后一点点。

提前致谢:-)

编辑：澄清一下。我会更详细地解释我需要什么。

我需要根据某些书籍属性对书籍进行分类。在这种特定情况下，我将一个字符串列表传递给该函数。我需要检查这些字符串是否包含在任何书名中。

所以首先，我认为我需要的 lambda 从一开始就是错误的。这是我实际需要的 lambda：b => values.Any(v => b.Title.ToString().Contains(v))

这是我得到的最终代码：

private static Expression<Func<Books, bool>> GenerateListContainsLikeExpression(string propertyName, List<string> values)
    {
        var parameter = Expression.Parameter(typeof(Books), "b");
        var listParameter = Expression.Parameter(typeof(string), "v");
        var property = Expression.Property(parameter, propertyName);
        var anyMethod = typeof(Enumerable).GetMethods(BindingFlags.Static | BindingFlags.Public).First(m => m.Name == "Any" && m.GetParameters().Count() == 2).MakeGenericMethod(typeof(string));
        var toStringMethod = typeof(object).GetMethod("ToString");
        var containsMethod = typeof(string).GetMethod("Contains");
        var objectString = Expression.Call(property, toStringMethod);
        var lambda = Expression.Call(objectString, containsMethod, listParameter);
        var func = Expression.Lambda<Func<string, bool>>(lambda, listParameter);
        var comparison = Expression.Call(anyMethod, Expression.Constant(values), func);

        return Expression.Lambda<Func<Books, bool>>(comparison, parameter);
    }

Answer 1

最终工作代码：

private static Expression<Func<Books, bool>> GenerateListContainsLikeExpression(string propertyName, List<string> values)
{
    var parameter = Expression.Parameter(typeof(Books), "b");
    var listParameter = Expression.Parameter(typeof(string), "v");
    var property = Expression.Property(parameter, propertyName);
    var anyMethod = typeof(Enumerable).GetMethods(BindingFlags.Static | BindingFlags.Public).First(m => m.Name == "Any" && m.GetParameters().Count() == 2).MakeGenericMethod(typeof(string));
    var toStringMethod = typeof(object).GetMethod("ToString");
    var containsMethod = typeof(string).GetMethod("Contains");
    var objectString = Expression.Call(property, toStringMethod);
    var lambda = Expression.Call(objectString, containsMethod, listParameter);
    var func = Expression.Lambda<Func<string, bool>>(lambda, listParameter);
    var comparison = Expression.Call(anyMethod, Expression.Constant(values), func);

    return Expression.Lambda<Func<Books, bool>>(comparison, parameter);
}

为了更深入地解释问题。请参阅我在原文中的编辑 post。

为 List.Any(v => v.Contains(Book.Title.ToString())) 生成表达式树

Generating Expression Tree for List.Any(v => v.Contains(Book.Title.ToString()))

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expression

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